In general, a liquid crystal display (“LCD”) device contains wiring such as scanning and signal lines, pixel electrodes, and switching elements such as thin film transistors. In order to make the wiring, electrodes and switching elements, thin films of conductive and dielectric materials are first formed on a substrate in a film-forming process. The thin films are then coated with a photoresist in a coating process. The coated thin films are optically exposed through patterned reticles in an exposing process. The exposed thin films are developed and etched in developing and etching processes, respectively, to remove the exposed thin films. These processes are repeated, if necessary, to form such wiring, electrodes and switching elements as designed.
With a recent trend of larger size LCD devices, a divided exposure process has been implemented. The divided exposure process is performed by dividing a large substrate into a plurality of regions and exposing in turn the regions through corresponding reticles. In the divided exposure process, there are regions with a width of 3μ to 10μ on divided lines. The regions are called multiple exposure regions, which are subject to a plurality of exposures in an overlapped exposing process.
Reticles as photomasks used for the divided exposure process are designed by employing a computer aided design (CAD) system. For design of reticle patterns, a pattern of an LCD panel size is determined in compliance with a design standard for an LCD device and, then, the pattern is divided depending on reticle sizes and the number of reticles. Here, division lines to divide the patterns are provided along places that have substantially no influence on LCD characteristics.
Further, design data on divided exposures of LCD panels are stored in a memory of the CAD system server. Based on the design data, reticle patterns are formed to meet requirements for design patterns of the LCD panels and division lines. Finally, light-shielding band patterns are added to the reticle patterns. The photomasks are completed in this way.
The substrate is exposed to form a plurality of LCD panel patterns through the photomasks, i.e., reticles positioned by using coordinates and other relevant data collectively called the exposure data. In other words, the exposure data contain ranges of exposure regions on the reticles, data indicating the center points as reference, coordinates data of the substrate to be exposed so that ranges designated on the reticles are exposed on the substrate (see Japanese Patent Disclosure 2002-367890, pages 2–4, and FIGS. 1–10).
When exposure data are, however, mistakenly entered into the CAD system for the divided exposure process, although such mistake may be found at an error processing step, it may not be detected until a pattern inspection step performed after patterns are exposed and formed on the substrate.
Further, when the division of reticles is made in error and boundaries between neighboring reticles are not consistent with each other, patterns formed on the substrate short-circuit or are broken so that the substrate is poor in quality. Particularly, when division lines are made zigzag in shape and are provided with buffer regions in order to make the lines hardly seen, it is not easy to find out patterns mistakenly formed on the substrate.